A biomaterial is a material tolerated by the human body which can be employed in the composition of a medical device. The contact between the biomaterial and the human body can be temporary, for the implementation of an image or images, or permanent, especially for the creation of an implant. This contact can relate to all or part of the biomaterial.
There is no knowledge in the prior art of a biomaterial constituted of at least one hydrophilic polymer and comprising a marker to have a signal different from that of the uncharged biomaterial and that of the biological environment in which it is placed. Known in the prior art are solely medical devices comprising a marker as well as contrast agents comprising a marker for magnetic resonance imaging.
Known in the prior art is, e.g., WO 94/23782, which pertains to medical devices such as catheters comprising nonmetallic members having paramagnetic ionic particles incorporated in the interior. The paramagnetic ionic particles are coated with a coating agent, the role of which is to retain water or any proton-donor liquid around the ionic particles since the medical device does not contain them. The results obtained are of very low significance: only a slight, not significant augmentation of the spin echo signal (T1, T2) and gradient echo signal is seen.
Also known is the preparation of colloidal magnetite solutions stabilized by different agents (Massart 1981, IEEE 17; Pouliquen and Chouly in “Microspheres microcapsules and liposomes 2”, for review).
Particles constituted of a polymer and iron oxide nanoparticles forming a superparamagnetic agent for the preparation of an injectable contrast agent to enable signalizing of e.g., hepatic tumors (cf. Fahlvik 1993, JMRI 3: 187-194; Chambon 1993 Magn Resol Imaging, 11: 509-519 are also known.
These contrast agents do not constitute a biomaterial in the classic sense of the term nor do they enable creation by themselves of a biomaterial.
The creation of a biomaterial for MRI is difficult and risky. In fact, if the superparamagnetic iron oxide particles are introduced directly into the material before polymerization, their distribution is inhomogeneous: they form aggregates and the signal obtained (image or extinction of image) is not processed because of the presence of numerous artifacts. It is necessary to be able to control the distribution in the biomaterial, i.e., the average distance between each marker grain to obtain precisely the desired signal.
It would therefore be advantageous to complex the superparamagnetic iron oxide particles with a hydrophilic polymer and to distribute them homogeneously in the hydrophilic polymer of the biomaterial to obtain a biomaterial having a specific signal different from that of the uncharged biomaterial and that of the biological environment in which it is placed.